Re: World War II Capacitors

From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Sent: 	Tuesday, July 01, 1997 8:31 AM
To: 	Tesla List
Subject: 	Re: World War II  Capacitors

Tesla List wrote:
> From:   Alan Sharp[SMTP:100624.504-at-compuserve-dot-com]
> Sent:   Monday, June 30, 1997 8:58 AM
> To:     INTERNET:tesla-at-pupman-dot-com
> Subject:        Re: World War II  Capacitors
> Greetings,
> I just aquired a couple of capacitors dated
> from 1945!
> They are inscribed:
> Admiralty pattern 1059
> Condenser Mica 0.0011MFD +/- 5%
> Tests A) 6 Amps at 300 KC - 1 hour
> B) 28000 volts D.C.
> max wkg condition approx 80% test condition
> Year 1945
> They are rectangular blocks about 2.5* 3.5 * 3
> inches. Bolt terminals on top.
> I think that these will still be good and that
> 10 in // will perform as well as a 0.01uf
> commercial capacitor at up to about 7kV AC.
> The guy wants L5 for them (about $7).
> Any comments - is this worth pursueing or should
> I stick to polythene and tinfoil.
> Have fun
> Alan Sharp (UK)


Buy all of them. and ask if he's got any more!! These are premium RF
transmitting capacitors, made from the highest quality single crystal
(not reconstituted) mica. High quality mica was used in high power
transmitting caps and was, at the time, the ONLY low-loss high voltage
dielectric available. Only the best of the best mica went into those
destined for government tranmitter use. 

Even though mica may have somewhat greater AC losses than LDPE, PS, or
PP, a mica cap can run all day at temperatures that will easily burn
your skin. A number of people on the list have used them quite
successfully primarily in tube coils... but that's because micas in
these voltage ranges are not that plentiful. They should work nicely in
disruptive use as long as you conservatively derate them, and your
derating to 1/4 of the WVDC rating is appropriate. 

Congratulations on a great find!

-- Bert H --